1. Field of Invention
The invention relates to a pump motor for a vehicle used for the purpose of supplying a washer liquid to a wiper apparatus mounted in a vehicle.
2. Description of Related Art
Generally, in this type of a pump motor housing, there are some pump motor housings in which a motor chamber is formed at the tip end side (upper side) via a partitioning wall, and a pump chamber is formed at the base end side (lower side). In such a type pump motor housing, it is necessary to form a ventilation hole, by which the inner atmosphere communicates with the outer atmosphere in order to make the inner and outer atmospheric air pressure uniform, in the motor chamber, but, at the same time, not permitting water to flow in. Therefore, conventionally, such a motor housing having a ventilation hole, has been proposed which communicates from the pump chamber side, i.e., adjacent the side of the pump chamber but external thereto, located at the lower side of the pump motor housing to the upper side motor chamber, the inner and outer atmospheric air being exchanged while avoiding invasion of water into the motor chamber. Such a housing, for example, is found in JP-Y2-62-20720. In the utility model, a ventilation hole that reaches from the outer diametrical portion at the base end side of the housing to the motor chamber is formed so as to bypass the pump chamber, and the ventilation hole is further opposed to a through hole opened at the outer diametrical portion of a covering member that seals and encloses the pump chamber, wherein the inner and outer atmospheric air of the motor chamber are caused to communicate with each other through the ventilation hole and through hole.
In the case where a housing, in which the ventilation hole described above has been formed, is formed integral therewith by using metal dies, the ventilation hole will be formed by inserting a draft die for the ventilation hole from the base end side, being the pump chamber side of the housing, to the motor chamber side. Generally the draft die is inserted almost parallel to the cylindrical center of a rough cylinder that forms the outer diameter of the housing. Therefore, it is necessary that the outer diameter of the motor chamber be made larger than the outer diameter of the pump chamber so that the ventilation hole penetrates from the outer diametrical side at the base end side of the pump chamber to the motor chamber.
On the other hand, recently, it is desired that a higher discharge pressure be provided from the pump chamber while downsizing the motor. To meet the requirement, it becomes necessary that impellers of the pump chamber are made large to have a large diameter while downsizing the diameter of the motor chamber. Therefore, in a case where such a housing is integrally formed by using the above-described metal dies, because the ventilation hole is formed at the outer side of the pump chamber although the diameter of the pump chamber is made larger than that of the motor chamber, the housing must have a large diameter over the full length of at least the portion where the ventilation hole is formed, wherein a problem arises, which hinders the downsizing thereof. Further, in such a case, because the shape of the covering member that clogs the opening at the base end side becomes complicated, a problem is caused in which the sealing property of the pump chamber, which becomes the inner diametrical portion at the base end side, may be damaged. An object of the invention resides in this point.
The invention was developed in order to solve the above problems in view of the above-described situations. It is therefore an object of the invention to provide a pump motor for a vehicle accommodated in a housing in which a motor chamber supporting a motor shaft is formed at the tip end side thereof and a pump chamber is formed at the base end side thereof via a partitioning wall, wherein, when forming a ventilation port or hole for communicating the interior of the motor chamber with the exterior thereof for venting so that the ventilation hole bypasses the pump chamber from the base end side of the housing to enter the motor chamber, an outer hole opened to the base end side of the housing communicates with an inner hole that is located closer to the axial center of the motor shaft than is the outer hole and is opened to the interior of the motor chamber, that is, the ventilation hole has a slope from the outer hole to the inner hole such that the outer hole is further from the axial center than is the inner hole.
With such a structure, the outer diameter opposed to the motor chamber of the housing can be formed to be small.
In such a pump motor, the inner hole and outer hole are produced by using split type upper and lower metal dies, and the communication between the inner hole and outer hole is formed through the fitting surface between the upper and lower metal dies.
Therefore, the ventilation hole is formed so as to incline and reach from the base end side of a projection, which protrudes from and is formed at the outer circumferential surface of the housing, opposite to the pump chamber, to the interior of the motor chamber.
Further, in this type of housing, a plurality of ventilation holes are formed in the circumferential direction of the housing, the respective ventilation holes are parallel to each other, and are formed in parallel to a plane passing through the motor shaft and a point midway between the outer holes of the ventilation holes.
Still further, in this type of housing, the projection according to the invention is formed adjacent to the circumferential direction with respect to an intake hole formed so as to protrude outward from the outer circumferential surface of the housing.
Still further, in this type of housing, a sealing recessed groove, to seal the pump chamber, is formed at the base end side of the housing, an inclined recessed groove inclined toward the inner side is formed adjacent to the outside of the sealing recessed groove, and the ventilation holes are positioned at both ends in the circumferential direction of the inclined recessed groove and are formed along the inclination of the inclined recessed groove.